Vacuum sanitary systems are known, and are used in many different connections in which conventional waste water systems are ineffective, or not workable. This is the case for example in ships, in which the vacuum sanitary system is widely used. One advantage of a vacuum system compared to a conventional system is that it is not necessary to lay the pipe system so as to enable a flow by gravity. Instead, in a vacuum system, it is an objective to lay the pipes so that water collecting parts, so-called pockets, are formed, which improve the transport of water. The system also permits waste water to be elevated to comparatively high levels through vertical pipe portions of the system. Another advantage is that the system can be built up of pipes of small dimensions, i.e. 50-100 mm, which facilitates assembling and laying of the piping. The so-called vacuum sanitary systems have been developed in the past by Sven Lilendahl who has been granted U.S. Pat. No. 3,239,849 issued Mar. 15, 1966, U.S. Pat. No. 3,181,553 issued May 4, 1965, U.S. Pat. No. 3,115,148 issued Dec. 24, 1963, U.S. Reissue Pat. No. 28,008 issued May 14, 1974 and U.S. Reissue Pat. No. 28,189 issued Oct. 8, 1974.
The known vacuum sanitary systems operate normally in accordance with some of the following three principles:
1. Waste, also called black water, from toilets and waste water, and so-called grey water, from other sanitary installations, are conveyed in separate systems and are collected in separate holding tanks.
2. Black water and grey water are conveyed in the same system and are collected in a common tank.
3. The black water is conveyed to a holding tank and the grey water is discharged by gravity directly to the ambient.
Common to the above methods in known systems is that they all require a collecting tank of a relatively large volume, in which at least the black water is collected. This tank is a pressure vessel which is under continual negative pressure by means of a vacuum pump. The volume of the tank is determined by specific requirement, but, as a rule, is about 3-6 m.sup.3. The tank functions as both storage for the waste water, and vacuum reserve for the pipe system.
The conduit for incoming waste water is connected to the upper part of the tank and to the sanitary installations by way of a pipe system. The sanitary installations, i.e. toilets, washstands, kitchen sinks and the like, are connected to the pipe system by valves which normally prevent the entrance of air into the system.
In operation, upon flushing of a toilet, the relevant valve opens a connection between the pipe system and the toilet bowl, the difference between atmospheric pressure, acting on one side of the liquid mass in the toilet bowl, and negative pressure in the pipe system acting at the other side of the liquid mass, causes the waste water to enter into and be conveyed in the system in the form of a plug. The valve is so constructed and arranged as not to close the connection immediately after the plug has passed but permits a given quantity of air to flow in after the plug.
The valve for controlling the grey water is usually located adjacent to the lower part of a washstand, a floor drain, or the like, and operates generally in the same manner as the black water valve. It is also common to collect grey water from several sanitary installations to one and the same valve. Thus, water coming from a washstand, a floor drain or the like is collected in a housing having a float which, when the water has reached a given level, acts on the valve to open the connection between the float housing and the pipe system so that grey water is discharged in the form of a plug. In addition, a given quantity of air is admitted together with the plug, so that the plugs will be well separated.
With the foregoing arrangement waste water will be moved forwards in the pipe system in the form of plugs, separated by air. When the conveying distance is long, the plug breaks during the transport, and the air behind it can flow past and the propelling force diminishes. To promote reforming of the plug in such cases it is possible, as stated above, to lay the pipe system so that pockets are formed to which waste water flows by gravity. In these pockets the pipe portion is filled up by the water and permits air behind the plug again to act on the plug so as to move it forwards in the system.
When the waste water and the air reach the tank, the air is discharged by the vacuum pump and the liquid is collected in the bottom of the tank.
It should be pointed out that it is extremely important in the transport of both black water and grey water that the above separation of the plugs is accomplished, since otherwise there is the risk that a system is obtained in which the plugs coalesce and form a long continuous water column. Such a column can become so large that it will block the operation of the entire system.
It should also be pointed out that it has been previously described in the literature to use a vacuum system for grey water which includes a fall pipe to which grey water is conveyed from washstands and the like. This pipe contains a standing liquid column which provides the required negative pressure in the system. The sanitary installations for the grey water include a float by which water is directly proportioned into the system without the mixing of air therein. However, the transport distance must be relatively small for this system to operate. When the described system is used, grey water will be conveyed very slowly through the transport conduit to the fall pipe, which involves a great risk of sedimentation and clogging in the conduits. For the above reasons it would not be possible to use this type of system for transport of black water, and therefore this system has not been applied in practice.
As indicated above, the disadvantages of the sanitary systems hitherto built for the said purpose are that the reception or holding tank is designed to hold a considerable quantity of water and thus has become large and bulky. This, in turn, means that both the cost of the proper tank and the cost of installation have become relatively high.
In order to overcome the above-mentioned drawbacks the present invention proposes a transport system which does not require a large vacuum tank. For this purpose, the invention is characterized in that waste water is transferred from the sanitary installations to the pipe system during simultaneous supply of air, and that the pipe system includes a generally vertical, comparatively long pipe, which is closed at its upper end. Waste water and air are introduced into the upper part of the pipe in such a manner that air is separated from waste water and is removed by the aid of a vacuum pump, or the like, connected to the said upper part, and in that the waste water is collected in the form of a standing liquid column in the lower part of the vertical pipe and is successively caused to flow to the reception or holding tank. Air is prevented from entering through the lower part of the pipe by means of a water seal, or the like. A device for carrying out the method in accordance with the invention is generally characterized in that the system of conduits includes a generally vertical, comparatively long pipe, whose lower end by a water seal, or the like, communicates with the reception tank, in which the pressure is below atmospheric pressure, and whose upper part communicates with a device that generates negative pressure.